GB2252518A

GB2252518A - Impact mill

Info

Publication number: GB2252518A
Application number: GB9123316A
Authority: GB
Inventors: Stephen Liebing
Original assignee: Buehler GmbH
Current assignee: Buehler GmbH
Priority date: 1991-02-06
Filing date: 1991-11-04
Publication date: 1992-08-12
Anticipated expiration: 2011-11-04
Also published as: IT1252143B; ITMI913216A1; DE4103468C2; GB9123316D0; US5292080A; GB2252518B; ITMI913216A0; DE4103468A1

Abstract

An impact mill specifically for grains and seeds includes a distribution head (4) rotatable in a housing (2) about an axis (3) to throw raw material against an impact body (17) surrounding the distribution head (4). The impact body (17) is rotatable about an axis (18) inclined to that of the distribution head (4) whereby wear on the impact body (17) by the material incident thereon from the distribution head (4) is equalised over the internal surface area thereof. As shown, the distribution head (4) is driven from below by a motor (8), and includes a horizontal disc (9) from which extend radial or curved blades. A mounting (16) for impact body (17) is arranged in a lid (2) and various constructions of body (17) are disclosed. The distribution head (4) may be secured to lid (2). Various driving arrangements are disclosed. Impact rings of varying heights/shapes may be utilised for different materials, and the angle of inclination ( alpha ) may be adjustable. <IMAGE>

Description

2252518 1 IMPACT MILL This invention relates to impact mills and more

particularly to such mills for impacting granular material such as grain, seeds and the like.

It is known to provide impact mills comprising a housing in which is mounted a distribution head driven to be rotatable about an axis and an impact body surrounding the distribution head also rotatable about an associated axis.

Impact mills of this type are either employed for crushincr tasks or as impact dehullers to separate the brittle shells from, for example, soybeans, cocoa beans or other huslit fruits, or, in general terms, to separate the seeds from the kernels.

In DE-C 529 396 there is disclosed an impact mill comprising a vertical driving shaft to which is attached a throwing rotor in the form of a distribution head. Coaxially with the driving shaft is arranged a cylindrical ly-shaped, stationary body closed at its lower end, said body comprising screen sections between which are located some beaters. The distribution head inr--.LL2----S F, dis,'k with blades on its circumference, the disc- Oeing 2 attached to the driving shaft to be inclined thereto.

Raw material is supplied through a drum sieve until the body or the drum sieve is almost f illed. The filling ratio is held constant during operation. Due to the particular construction and operation of the mill, the raw material emitted by the lower blade is not capable of exerting any impact ef fect upon the beaters and the drum sieve, as this blade solely digs through the raw material. Thus, an impact effect is only exerted by the upper blade. As a result, the wall of the drum sieve will be subjected to irregular wearing.

US patent specification no. 2 352 327 discloses a further impact mill, in which a.distribution head rotatable about a vertical axis of rotation and a cylindrical impact ring arranged coaxially with the distribution head are both driven but at different speeds. The lower side of the impact ring is supported by toothed wheels meshing with the impact ring. By designing this lower region of the impact ring to have a wavelike configuration, oscillating vertical motion of the impact ring is achieved whereby uniform wear of the annular lining exchangeably fastened to the impact ring will occur as a result of extending the surface of the impact ring hit by the particles, thus resulting in a longer service life of the mill.

The drawbacks of this construction are that it is more expensive to produce and it is difficult to guide the impact ring within the housing, since, with this particular construction, tilting of the ring will probably occur. in addition, the upper and lower dead points of the wave 3 curves will lead to a longer biasing 6f the impact ring at those points, thus entailing an irregular wear of the annular coating.

It would be desirable to be able to provide an impact mill eliminating the aforementioned drawbacks and in which the impact body is subjected to uniform wear in a constructionally simple manner. - According to the present invention there is provided an impact mill comprising a housing in which is mounted a distribution head rotatable within the housing about an axis extending longitudinally of the housing, an impact body surrounding the distribution head and rotatable about an associated axis, the axes of rotation of the distribution head and the impact body being inclined to one another.

Such an arrangement enables a cheaper and constructionally simpler mill than heretofore to be provided, the regular wear of the annular coating to the impact body that occurs -resulting in the service life of the impact body being increased and, consequently, more economical operation of the mill.

More particularly, the jet of particles omitted by the distribution head will stroke over different surface regions of the impact body when this is being rotated, whereby wear is distributed over the whole of the surface area of the impact body.

Preferably the axis of rota tion of the distribution head is vertical, while it is further preferred that the distribution head defines therein. at least one discharge 4 opening therefrom, the or each discharge opening being situated in a horizontal plane.

Although the aigle of the impact body could periodically be manually adjusted, it is preferred that the impact body is driven by a motor incorporating a reduction gear unit.

Although a large angle of inclination could exist between the two axes of rotation, particularly if the impact body was not exactly cylindrical for example spherically bulged - it is preferred that the angle of inclination between the axes of rotation of the 0 distribution head and the impact body does not exceed 20 while it is further preferred that said angle of inclination falls within the range of 13 0 to 170.

By way of example only an embodiment of the invention will now be described in greater detail with reference to the accompanying drawing which is a vertical section through an impact mill according to the invention.

Referring to the drawing, the impact mill comprises a cylindrical housing 1 which can be closed by means of a lid 2 attached to the housing 1 to be capable of swinging or swivelling about an axis of rotation.

A distribution head 4 is mounted in the housing 1 to be rotatable about an axis 3 passing centrally of the housing 1 through an upper feeding pipe 5 for the raw material, through the housing 1, and through a lower discharge pipe 6 from the housing 1. The distribution head 4, which can be driven from below by a motor 8 enclosed in a metallic sheathing, is axially fixed but rotatable in the 1 housing 1, and includes a horizontal disc 9 upwardly f rom which extend radial or curved blades. The precise construction of the distribution head can be varied f rom that shown for example, instead of employing only one disc, two tubular centrifugal arms arranged one to each side of the rotational axis 3 may be provided. In all cases, the discharge openings 10 of the distribution head 4 lie in a horizontal plane.

A mounting 16 f or an impact body 17 is rotatably arranged in the lid 2, the axis of rotation 18 of the impact body being inclined relative to the axis of rotation 3 when the lid 2 is closed, such that the two axes of rotation 3,18 intersect one another at an angle alpha.

It is advantageous for the point of intersection of the two axes 3,18 to be located in the same horizontal plane as the distribution head 4, as illlustrated., so that the distances of the discharge openings 10 of the distribution head 4 f rom the impact body 17 will vary only within a relatively small range when the impact body 17 is rotating relative to the distribution head 4. The angle formed by the two axes 3,18 depends upon the diameter of the disc 9 and on the height and diameter of the impact body 17, as well as, possibly, on the shape (cylindral or curved) of the impact body 17. The impact body 17 may alternatively comprise straight metal plates, if necessary provided with a rubber lining, which metal plates are arranged to surround the axis of rotation 3 in a stationary or movable way. Examples of such impact bodies are disclosed in, for example, DE-B-1 195 144, DE-A-23 50 220 and DE-C-30 11 112, 6 the entire disclosures of vhich are incorporated herein by reference. It is advantageous to provide a counter-move member, or damping element 28 to compensate for the weight of the lid.

An upper bearing body 15 is provided on the lid 2 to support the rotatable impact body- on the lid 2, said bearing body 15 being attached to the lid 2, while the distribution head 4 is preferably firmly connected to a stationary part of the housing 1. Of course, it is also possible to secure the distribution head 4 to the lid 2. In such a case, the distribution head 4 could be swung onto a driving cone of the motor 8 when the lid 2 is hinged downwardly so as to effect a driving connection between the motor and the head 4. The feeding pipe 5 may also be firmly connected to the lid 2. in another possible construction, the feeding pipe 5 is detached when the lid 2 is swung open.

It is advantageous for the mounting 16 carrying the impact ring 17 to be driven at a slow rotational speed. To this end, a gear rim 19 is provided coaxial with the axis of rotation 18 between mounting 16, to which the impact body 17 is clamped, and an end cap 20 of the lid 2. The gear rim 19 engages a pinion 22 driven by a motor 21 incorporating a reduction gear unit 12 and mounted on the outside of end cap 20.

Clearly, it would also be possible to provide a V-belt drive, or any other driving arrangement to the gear rim 19 but - in all cases it is advantageous to design the associated drive wheel -gear rim 19 with a central opening 7 27 through which the raw material can be supplied. In the illustrated case this will take place via feeding pipe 5. To keep the latter in as vertical a position as possible, it is convenient to make opening 27 encompass both of the axes 3,18 at a certain distance from them. If necessary, a ratchet mechanism may also be used for turning the impact ring 17. In this way, the problem of supply of material will be solved in a simple manner, in spite of diverging axes of rotation.

From the drawing it will be apparent that the outlet from the left part of disc 9 is directed to a section of the upper edge of the impact body 17, and the outlet from the right part of disc 9 is directed to a section of the lower par t of body 17. In between the lef t and right parts, the disc 9 faces the central portions of the impact body. With just slow rotational speed of the impact body 17, f or example two revolutions per minute, all of the sections of all height levels of the impact body 17 will be impacted in a uniform way.

In order to prevent dead corners f rom developing in the impact body (such as at the top lef t in the drawing), in which impacted material may settle, it is preferred to provide clearances 26 in the marginal area of the mounting 16 next to impact body 17, so that the raw material can pass upwards and thereafter outwards of the impact body 17 to discharge pipe 6.

In order to connect gear rim 19 to the impact body 17, the former is firmly linked to a disc 13, which, in turn,is connected to the mounting 16 by a small web 14 defining 8 the openings 26. -The impact body 17 is detachably fastened to the disc 13 by a closing member 23 extending into a clamping ring 24 attached to the impact body 17.

Within the scope of the invention, numerous modifications are conceivable. For. example, if impact rings of varying heights (possibly also of varying shapes) for different raw materials arb to be employed, it may be desirable to make the angle alpha adjustable. This may be done by rendering the height of the lid 2 and the housing 1 adjustable by means of an adjusting spindle, or by incorporating a plurality of selectively usable catches for the closed position of the lid, with any possible gap in between the housing 1 and the lid 2 being obtainable by a telescopically displaceable intermediate part connected to the housing or the lid.

9 1

Claims

1. An impact mill comprising a housing in which is mounted a distribution head rotatable within the housing about an axis extending longitudinally of the housing, and an impact body surrounding the distribution head and rotatable about an associated axis, the axes of rotation of the distribution head and the impact body.being inclined to one another.

2. An impact mill as claimed in claim 1 in which the axis of rotation of the distribution head is vertical.

3. An impact mill as claimed in claim 2 in which the distribution head defines therein at least one discharge opening therefom, the or each discharge opening being situated in a horizontal plane.

4. An impact mill as claimed in any one of claims 1 to 3 in which the impact body is driven by a motor incorporating a reduction gear unit.

5. An impact mill as claimed in any one of claims 1 to 4 in which the angle of inclination between the axes of rotation of the distribution head and the impact body 0 does not exceed 20

6. An impact mill as claimed in claim 5 in which said angle of inclination falls within the range'of 13 0 to 17 0.

7. An impact mill as claimed in any one of claims 1 to 6 in which the axes of rotation intersect one another in the plane of the distribution head.

8. An impact mill as claimed in any one claims 1 to 7 and comprising a lid for the top of the housing movable between a closed position on the housing and an open position permitting access to the distribution head within the housing, the lid carrying bearing means for rotatably supporting the impact body within the housing.

9. An impact mill as claimed in claim 8 in which the distribution head is axially fixed within the housing.

10. An impact mill as claimed in claim 8 or claim 9 and including material supply means feeding to the distribution head, said supply means comprising a tube connected to the lid.

11. An impact mill as claimed in any one of claims 8 to 10 in which the bearing means carry holding means for supporting the impact body and a gear rim by which the impact body can be rotated, pinnion means engaging with the gear rim to effect said rotation.

12. An impact mill as claimed in claim 11 together with claim 10 in which the gear rim incorporates a central opening through which the material supply means projects.

13. An impact mill as claimed in claim 12 in which the axes of rotation of the distribution head and the impact body both extend through said central opening in the gear rim.

14. An impact mill as claimed in any one of claims 1 to 13 in which the impact body comprises an annular side-wall and a top wall on said sidewall, said top wall being provided with at least one aperture therein adjacent the sidewall for passage therethrough of material from within the impact body.

15. An impact mill as claimed in claim 14 in which the top wall of the impact body includes a thin web 1 11 defining therein at least two opposed apertures.

16. An impact mill substantially as described with reference to and as illustrated by the accompanying drawing.